title: PUA - Netcat Suspicious Execution
id: e31033fc-33f0-4020-9a16-faf9b31cbf08
status: test
description: Detects execution of Netcat. Adversaries may use a non-application layer protocol for communication between host and C2 server or among infected hosts within a network
references:
    - https://nmap.org/ncat/
    - https://github.com/redcanaryco/atomic-red-team/blob/f339e7da7d05f6057fdfcdd3742bfcf365fee2a9/atomics/T1095/T1095.md
    - https://www.revshells.com/
author: frack113, Florian Roth (Nextron Systems)
date: 2021-07-21
modified: 2023-02-08
tags:
    - attack.command-and-control
    - attack.t1095
logsource:
    category: process_creation
    product: windows
detection:
    selection_img:
        # can not use OriginalFileName as is empty
        Image|endswith:
            - '\nc.exe'
            - '\ncat.exe'
            - '\netcat.exe'
    selection_cmdline:
        # Typical command lines
        CommandLine|contains:
            - ' -lvp '
            - ' -lvnp'
            - ' -l -v -p '
            - ' -lv -p '
            - ' -l --proxy-type http '
            # - ' --exec cmd.exe ' # Not specific enough for netcat
            - ' -vnl --exec '
            - ' -vnl -e '
            - ' --lua-exec '
            - ' --sh-exec '
    condition: 1 of selection_*
falsepositives:
    - Legitimate ncat use
level: high

title: Netcat The Powershell Version
id: c5b20776-639a-49bf-94c7-84f912b91c15
related:
    - id: bf7286e7-c0be-460b-a7e8-5b2e07ecc2f2
      type: derived
status: test
description: Adversaries may use a non-application layer protocol for communication between host and C2 server or among infected hosts within a network
references:
    - https://nmap.org/ncat/
    - https://github.com/besimorhino/powercat
    - https://github.com/redcanaryco/atomic-red-team/blob/f339e7da7d05f6057fdfcdd3742bfcf365fee2a9/atomics/T1095/T1095.md
author: frack113
date: 2021-07-21
modified: 2023-10-27
tags:
    - attack.command-and-control
    - attack.execution
    - attack.t1095
    - attack.t1059.001
logsource:
    product: windows
    category: ps_classic_start
detection:
    selection:
        Data|contains:
            - 'powercat '
            - 'powercat.ps1'
    condition: selection
falsepositives:
    - Unknown
level: medium

title: Suspicious DNS Z Flag Bit Set
id: ede05abc-2c9e-4624-9944-9ff17fdc0bf5
status: test
description: |
    The DNS Z flag is bit within the DNS protocol header that is, per the IETF design, meant to be used reserved (unused).
    Although recently it has been used in DNSSec, the value being set to anything other than 0 should be rare.
    Otherwise if it is set to non 0 and DNSSec is being used, then excluding the legitimate domains is low effort and high reward.
    Determine if multiple of these files were accessed in a short period of time to further enhance the possibility of seeing if this was a one off or the possibility of larger sensitive file gathering.
    This Sigma query is designed to accompany the Corelight Threat Hunting Guide, which can be found here: https://www3.corelight.com/corelights-introductory-guide-to-threat-hunting-with-zeek-bro-logs'
references:
    - https://twitter.com/neu5ron/status/1346245602502443009
    - https://tdm.socprime.com/tdm/info/eLbyj4JjI15v#sigma
    - https://tools.ietf.org/html/rfc2929#section-2.1
    - https://www.netresec.com/?page=Blog&month=2021-01&post=Finding-Targeted-SUNBURST-Victims-with-pDNS
author: '@neu5ron, SOC Prime Team, Corelight'
date: 2021-05-04
modified: 2022-11-29
tags:
    - attack.t1095
    - attack.t1571
    - attack.command-and-control
logsource:
    product: zeek
    service: dns
detection:
    z_flag_unset:
        Z: 0
    most_probable_valid_domain:
        query|contains: '.'
    exclude_tlds:
        query|endswith:
            - '.arpa'
            - '.local'
            - '.ultradns.net'
            - '.twtrdns.net'
            - '.azuredns-prd.info'
            - '.azure-dns.com'
            - '.azuredns-ff.info'
            - '.azuredns-ff.org'
            - '.azuregov-dns.org'
    exclude_query_types:
        qtype_name:
            - 'ns'
            - 'mx'
    exclude_responses:
        answers|endswith: '\\x00'
    exclude_netbios:
        id.resp_p:
            - 137
            - 138
            - 139
    condition: not z_flag_unset and most_probable_valid_domain and not (exclude_tlds or exclude_query_types or exclude_responses or exclude_netbios)
falsepositives:
    - 'Internal or legitimate external domains using DNSSec. Verify if these are legitimate DNSSec domains and then exclude them.'
    - 'If you work in a Public Sector then it may be good to exclude things like endswith ".edu", ".gov" and or ".mil"'
level: medium